1. Field of the Invention
The present invention relates generally to a medical device designed to enhance performance and reduce the risk of injury to the knee. Comprised of a flexible sleeve with strategically positioned hamstring and knee buttresses, the Anterior Cruciate Ligament Tube (“ACL Tube”) of the present invention is designed to be worn during periods of physical activity or while at rest. In a preferred embodiment, each component of the ACL Tube is composed of resilient, non-rigid material, and the invention increases proprioception and reduces the risk of injury by applying pressure to the hamstring muscles and/or the Vastus Medialis Obliquus (“VMO”) of a human subject.
2. Discussion of the Background
Injuries to the Anterior Cruciate Ligament (“ACL”) are among the most feared by athletes of any sport. This year alone, it is estimated that over a quarter million people will tear their ACL. Roughly 70% of these injuries will require surgical reconstruction at a cost of $17,000 to $25,000 per injury. Indeed, injuries to the ACL are the most common knee ligament injuries. Although the affected individual is able to return to sports in 80-95% of cases, the long-term effects of an ACL tear negatively impact one's quality of life for many years thereafter.
One skilled in the art recognizes that the term “knee” refers to the complex synovial joint in humans that joins the thigh with the leg and consists of two articulations: one between the femur and tibia, and one between the femur and patella. The knee actually comprises three functional compartments: the femoropatellar, or “kneecap”, the patellar groove; and the medial and lateral femorotibial articulations linking the femur, or thigh bone, with the tibia, the main bone of the lower leg.
The ACL is one of the four primary ligaments in the human knee (the others being the medial collateral ligament, the posterior cruciate ligament, and the lateral collateral ligament). As used herein, the term “knee injury” refers to a tear, rupture, or other injury to one or more of these ligaments, or to any dislocation, tracking, or other injury to the patella. The ACL extends between the “notch” of the distal femur and the medial wall of the lateral femoral condyle. The two fibrous bundles comprising the ACL are named for where they attach to the tibial plateau: the anteromedial and the posterolateral. The ACL attaches to the (anterior) intercondyloid eminence of the tibia, where it blends with the anterior horn of the lateral meniscus. These attachments provide stability to the knee joint by preventing anterior translation of the tibia in relation to the femur.
Interestingly, ACL tears occur disproportionately among women. Research indicates that women who participate in comparable jumping and cutting athletic activities tear their ACL two-to-nine times more often than their male counterparts. Experts have advanced a number of theories to explain this imbalance, including relative differences in environment, lower limb alignment, muscular strength, jump biomechanics, neuromuscular traits, hormone levels, and fitness level (conditioning). According to one theory, women experience higher rates of ACL tears because their hamstrings and quadriceps contract in a different order and at a different rate than do those of men. When men return to the ground after a vertical jump, their hamstrings generally contract before their quadriceps. This keeps the tibia posterior and protects the ACL from injury. When many women return to the ground after a vertical jump, however, the quadriceps fire first and the knee rotates internally. This physiological response places excessive strain on a woman's knees and may cause injury to her ACL. Thus, knee abduction loading appears to be a critical factor that contributes to the rupture of the ACL. Female athletes generate greater abduction loads when cutting and landing (compared to their male counterparts).
It is therefore hypothesized that knee abduction is a critical factor that contributes to the increased incidence of ACL injuries among women. See, e.g., Palmieri-Smith et. al, “Association of Quadriceps and Hamstrings Cocontraction Patterns with Knee Joint Loading”, Journal of Athletic Training, 2009; 44(3):256-63.
The above study found that women experience lower overall quadriceps-to-hamstrings (Q:H) cocontraction, and that medial-to-lateral Q:H cocontraction appears to be particularly unbalanced in women. This imbalance limits the ability of female athletes to resist abduction loading. This may account for the added incidence of ACL injuries among women, because increased abduction loads create added strain on the ACL. In other words, the experimental and epidemiological evidence suggests that female athletes unwittingly utilize a selective Q:H activation strategy that contributes to abduction loading—a critical factor in the ACL rupture mechanism. Rather than evenly cocontracting the muscles that control abduction loading, women appear to contract the lateral quadriceps and hamstrings while underactivating the medial thigh muscles. Selective activation of the medial knee muscles helps to resist abduction loads. Thus, the pattern of Q:H contraction in women appears harmful to the ACL. In contrast, balanced cocontraction of the quadriceps and hamstrings (in the so-called frontal plane) enhances joint compression, which increases the stability of the knee joint. Overall, the existing research indicates that Q:H cocontraction is lower among female athletes as compared to their male counterparts.
Moreover, women typically have wider hips and a smaller femoral “notch” (to which the proximal end of the ACL attaches). These unique physiological and biomechanical characteristics observed among female athletes often cause greater internal rotation of the knee and result in an increased incidence of ACL injuries.
Unfortunately, contemporary athletic training programs and orthopedic devices fail to compensate for these unique female characteristics. Existing knee braces and athletic training methods utilize “one-size-fits-all” solutions that all too often focus on men to the exclusion of women. A need exists, therefore, for a device and training method designed to address the unique neurophysiological relationship between the quadriceps, hamstrings, and the ACL in women. Specifically, a need exists for a proprioceptive knee device configured to lower the risk of knee injuries, especially in women athletes. Such a device would preferably enhance neuromuscular communication to coordinate hamstring and quadriceps contraction in women to lower the risk of knee injuries.